The present invention generally relates to a method, system, and program for monitoring and controlling a fluid transportation system. More specifically, the present invention is directed to a medium readable by a programmable device. The medium being operably connected to a controller for monitoring and controlling a fluid flow volume in a fluid transportation system.
The production, transportation and sale of energy sources has always required some form of measurement to determine the quantity produced, bought, or sold. The accuracy and reliability of a system that measures an energy source, i.e., gas and liquid, is extremely important to the buyers and sellers involved. A seemingly insignificant error within the measuring system can result in a large monetary loss.
Technological advances in the areas of fluid flow metering and computation has led to improved accuracy and reliability. Some of these advances have been made in the area of metering, or measuring, transported energy products. These advances have also focused on factors such as safety, reliability and standardization.
Today""s metering and transfer system involves more than simply measuring fluid flow; it can also involve extensive electronics, software, communication interfaces, analysis, and control. Measuring fluid flow can involve multiple turbine meters with energy flow computers, densitometers, gas chromatography, meter proving systems and RTU or SCADA interfaces.
Measurement and control of energy sources are valuable processes for companies producing and transporting theses energy sources. Many governments, organizations and industries have enacted standards and regulations related to recovering, refining, distributing, and selling of oil and oil by-products, i.e., gasoline, kerosene, butane, ethanol, etc. The energy resource industry has various standards and regulations to ensure the accuracy and safety of transporting and metering these energy sources.
The process of transporting a fluid energy source, e.g., oil, through a pipeline is monitored and controlled with the assistance of a combination of sensors and process computers. Generally, a computer processor monitors several aspects, e.g., fluid flow volume, of the oil transportation. The control of the equipment facilitating the transportation of oil is generally performed by environmentally robust devices such as a controller. The controller regulates valves, tanks, and scales without requiring an individual to constantly interact with the system.
A very important aspect of a fluid transportation system involves the fluid flow meter utilized to monitor the amount of oil delivered to a customer. Because of the vast amounts of fluid delivered, the accuracy of the fluid flow meter must be ensured at regular intervals. An inaccurate fluid flow meter can result in overcharging or undercharging a customer for the delivered product. An inaccurate flow metering system can result in significant amounts of unpaid products, i.e., shrinkage.
A turbine flow meter is an accurate and reliable flow meter for both liquid and gas volumetric flow. Some applications utilizing a turbine flow meter involve water, natural gas, oil, petrochemicals, beverages, aerospace, and medical supplies. The turbine comprises a rotor having a plurality of blades mounted across the flow direction of the fluid. The diameter of the rotor is slightly less than the inner diameter of a conduit, and its speed of rotation is proportional to the volumetric flow volume through the conduit. Turbine rotation can be detected by solid state devices or mechanical sensors.
In one application utilizing a variable reluctance coil pick-up, i.e., a permanent magnet, turbine blades are made of a material attracted to the magnet. As each blade of the turbine passes the coil, a voltage pulse is generated in the coil. Each pulse represents a discrete volume of liquid. The number of pulses per unit volume is called the meter""s K-factor.
In another application utilizing inductance pick-up, a permanent magnet is embedded in the rotor. As each blade passes the coil, a voltage pulse is generated. Alternatively, only one blade is magnetic and the pulse represents a complete revolution of the rotor. Depending upon the design, it may be preferable to amplify the output signal prior to its transmission.
The accuracy of a turbine flow meter partially depends upon proving the fluid flow meter and the ability to provide correction factors to compensate for meter inaccuracies caused by damage to the meter or surrounding environmental conditions. At a minimum, a typical flow computer utilizes the following industrial standard volume flow equations to determine the correction factors. The American Petroleum Institute defines the API 2540 standard to determine flow of liquid hydrocarbons that includes the following techniques: meter proving; correction for temperature, density (fluid gravity) and pressure of the fluid flowing; pulse interpolation; pulse fidelity; correction for the temperature and pressure of the conduit material (typically steel); and audit trails and report specifications. The American Society for Testing and Materials that defines the ASTM D1250 and the American National Standards Institute that defines the ANSI D1250 standard have adopted, in their respective industry segments, the API 2540 standards. The American Petroleum Institute also defines a M factor used to correct for the loss of turbine accuracy. Over time, the turbine becomes less accurate due to wear and tear; and the M factorxe2x80x94a dimensionless numberxe2x80x94incorporated into the API 2540 equations adjusts for turbine inaccuracy. API 2540, ASTM D1250 and ANSI D1250 are expressly incorporated herein by reference.
Proving the fluid flow meter is a process for ensuring the accuracy and reliability of the flow meter. Typically, a section of the fluid system called a proving loop is utilized during the meter proving. The dimensions of the proving loop are known and the flow of fluid within the loop can be monitored by sensors wherein a variety of fluid characteristics can be sensed. The meter proving process simultaneously monitors a pulse signal generated by a turbine operably connected within the fluid system. The flow volume of the fluid is determined by utilizing the sensed values of the fluid""s characteristics with the industrial standard flow volume equations. The calculated flow volume is then compared to the known flow volume of the proving loop. By comparing the calculated fluid flow volume to the known fluid flow volume of the proving loop, the accuracy of the flow meter can be determined.
Generally, the duration of a meter proving process is approximately one hundred thousand turbine pulses. This amount of time is believed to be adequate to accurately determine the fluid flow volume. Often times, the turbine pulse signal is not in synch with the flow meter proving process, i.e., generally the meter proving process will not start at the beginning of the turbine pulse signal. When the pulses are counted at the end of the proving period, the partial pulses occurring at the beginning and end of the proving period are omitted. Because of the duration of the proving period, it is generally believed that these partial pulses are negligible. However, utilizing the partial pulses and other characteristics of the fluid and conduit, the time required for the meter proving process can be reduced.
This invention is directed to solving these and other problems.
The present invention is directed to utilizing a software program operable within a controller to monitor a flow volume in a fluid transportation system. The software interacts with the controller, e.g., programmable logic controller (PLC), and an operably connected flow meter to sense a characteristic of the fluid for calculating the fluid flow volume of the liquid. The sensed characteristic of the fluid, e.g., temperature, density, and pressure; is utilized by the software program to determine correction factors to be incorporated with industrial standard equations. The software program also includes an interpolation method for any partially sensed revolutions of the flow meter occurring during a meter proving process. The software program provides correction factors to the flow meter via the controller and its turbine meter module. The supplied correction factors adjust the flow meter for any inaccuracies; thereby, reducing product shrinkage. The resultant correction factors, in communication with the turbine meter card, provide a less expensive implementation for controlling and monitoring a fluid transportation system without the need of a separate fluid flow computer.
One embodiment of the present invention is directed to a system for calculating a flow volume of a fluid within a conduit having an operably connected flow meter. The system comprises a programmable logic controller having a backplane. A flow meter module is operably connected to the backplane of the programmable logic controller and to the flow meter. A program operably connected within the programmable logic controller includes a plurality of segments for cooperating with the flow meter to sense a characteristic of the fluid. Data received from the flow meter is utilized by the program to calculate the flow volume of the fluid within the conduit.
In a further aspect of the present invention, the fluid characteristic sensed by the flow meter is temperature, pressure, and/or density. The sensed characteristic is utilized by the controller to provide a real-time update of an industrial correction factor wherein the computation of the fluid flow volume is adjusted in response to the sensed characteristic. Alternatively, characteristics of the conduit can also be monitored and utilized by the controller to provide real-time updates of the industrial correction factor.
A further embodiment of the present invention is directed to a method of measuring a flow volume of a fluid within a conduit. A controller is connected to a flow meter and the conduit. The controller monitors the fluid flow volume through a plurality of input channels operably connected to the flow meter of a fluid transportation system. The controller senses a pulse signal generated by the flow meter over a predetermined time frame. A densitometer operably connected to the controller senses the real time density of the fluid. The sensed density is stored by the controller as a dynamic variable to be utilized in the determination of the flow volume. The controller utilizes the sensed dynamic density in cooperation with the standard industrial equations, AGA-7/API 2540, for calculating a flow volume.
In another embodiment of the present invention, a medium for calculating a flow volume of a fluid within a conduit is disclosed. The medium is readable by a programmable logic controller being operably connected to a flow meter and a conduit. The medium includes a program comprising several segments cooperating to determine the flow volume of a fluid. A first segment obtains a characteristic of the fluid. The characteristic being temperature, pressure, and/or density. A second segment utilizes an industrial standard equation, API 2540, to calculate a correction factor in response to the sensed fluid characteristic. And a third segment calculates a meter correction factor in response to a meter proving.
Another embodiment of the present invention is directed to a method of proving a flow meter. The flow meter is connected to a controller and a proving loop within a fluid transportation system. The proving loop has a known flow volume. The controller monitors a fluid flow within the proving loop. The method comprises the steps of starting a meter proving period and sensing a pulse signal responsive to a flow meter. The flow meter generates a fluid flow through the fluid transportation system. The meter proving process is terminated and the amount of sensed pulse signals occurring during the meter proving period is calculated. The fluid flow volume of the proving loop is determined in response to the pulse signals occurring during the meter proving process and other sensed characteristics of the fluid and conduit, preferably density and temperature. The calculated flow volume of the proving loop is compared against the known volume of the proving loop.
A further aspect of the above embodiment of the present invention is directed to adjusting the flow meter and/or controller in response to the comparison of the calculated flow volume of the proving loop and its known flow volume, wherein the fluid flow meter and/or controller more accurately calculate the flow volume.
An object of the present invention is to utilize standard industrial equations embedded within the programmable logic controller, rather than incorporated within a remote I/O device such as a flow computer, to reduce the time and cost of meter proving and to improve the accuracy when calculating the fluid flow rate of a liquid within a conduit. The use of frequently updated correction factors with the meter flow equations improves the accuracy and reliability of the flow meter. The controller senses real-time process variables, e.g., fluid and conduit characteristics used in the standard flow equations, and calculates a more accurate correction factor. Because the programmable logic controller monitoring and controlling the metering process utilizes the correction factor more frequently, shrinkage will be reduced.
Cost savings are obtained because the programmable logic controller replaces the flow computer, as a remote I/O device. Removing the flow computer as an I/O device from the already present PLC reduces cost and inaccuracy. In place of the flow computer, the system uses existing I/O to measure characteristics, such as, density, temperature and pressure of the flowing fluid and of the conduit material encapsulating the fluid. The PLC adds flexibility because characteristics affecting the fluid (stated above in this paragraph) are resident in the memory of the PLC. Other features of the PLC such as processing speed; tables containing standards; and remote web access can be added without difficulty. Moreover, the PLC can store past values to help ensure repeatability already inherent in a fixed, stable system that a PLC offers. In addition, more accurate flow volume calculations can be obtained by utilizing additional characteristics of the fluid and conduit, i.e., real time density, temperature, and pressure values, in cooperation with the industrial standard equations of API 2540/AGA-7.
Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention.